1. Field of the Invention
This invention relates to pivotal joints wherein two joined members are pivotal relative to one another and wherein the joints include redundant pivot connections therebetween so that a secondary pivot connection becomes operative should the primary pivot connection be lost, for example due to ballistic damage.
2. Description of the Prior Art
U.S. Pat. No. 4,030,378 is probably representative of and the closest prior art. It teaches a construction wherein two pivotally joined parts have a primary pivot bolt connection therebetween and a secondary pivot connection in the form of bolt-in-slot connection which serves as a redundant pivot connection if the primary pivot connection fails. This prior art construction may also utilize two bolt-in-slot connections spaced about 90.degree. apart. This prior art construction, while adequate in operation, tends to require a large space envelope, and such a relatively large space envelope is not always available in some installations such as flight control systems of aircraft, including helicopters. Additional disadvantage of this prior art construction which the present invention overcomes is that the secondary pivot support mode is considerably less stable than the primary pivot support mode, the degree of pivot motion is restricted by the arc of the slot, it is a heavier construction and requires a greater number of parts. This slot and pin prior art construction has limitations with respect to the self-aligning capability of the joint and cannot therefore be used on a non-planar linkage unless the clearance between the slot and pin are substantial. This substantial clearance, of course, results in a sloppier joint when in the secondary mode of operation.